Sensing device



April 1963 R. c. PITNEY 3,377,842

SENSING DEVICE Filed July 12, 1965 Er 7 I11: 71 /7 13 E S INVENTOR.

Robert C. Pi-Tncy BY United States Patent 3,377,842 SENSING DEVICE Robert C. Pitney, Stamford, Conn., assignor to Pitney-Bowes, Inc, Stamr'ord, Comm, a corporation of Delaware Filed July 12, 1965, Ser. No. 471,249 1 Claim. (Cl. 7337) ABSTRACT OF THE DISCLOSURE A method of sensing the presence of a sheet wherein a strong fluid jet is coaxially directed against a weaker fluid jet so that when a sheet is introduced between said jets the static pressure in said weaker fluid jet will drop and may be sensed independently of the pressure in said strong jet so as to indicate the presence of said sheet.

This invention relates to an improved fluid operating sensing device. More particularly the invention relates to a novel means for initiating a pneumatic signal in response to a disruption in a given set of normal fluid flow conditions.

There are many situations Where it is desirable to use fluid jets to sense the presence and/ or absence of an object at a particular location. Where such jets are so used however there is an ever present possibility that the fluid conduit lines, valves, orifices, etc. associated therewith can become clogged or otherwise contaminated by foreign matter such as dust which might find its way into the fluid system. Various techniques such as filtering have been used in an effort to minimize the contamination problem here; however in most cases these techniques have not been satisfactory because of the attendant disadvantage of either increased costs or decreased reliability resulting from added complexity, or both. The instant invention contemplates a simple non-contaminating system and arrangement of fluid jets and associated circuitry for reliably detecting the presence of an object at a predetermined location.

Accordingly the primary object of the invention is to provide a novel sensing system wherein a pair of opposed fluid jets are operatively directed at each other so that a pressure change occurs in the fluid conduit means associated with at least one of said jets when an object to be sensed is placed in intercepting relation with respect to the other of said jets.

Another object of the invention is to provide a novel method and apparatus for detecting the presence of an object at a predetermined location whereby a first jet of fluid from an emitter is directed towards a receiver opening that also issues a second jet of fluid which is eflectively weaker than said first jet of fluid, the interruption of said first jet by an object placed between the emitter and receiver opening serving to cause a pressure drop at a point upstream in said second jet of fluid.

Other objects will become apparent as the disclosure progresses.

In the drawings:

FIG. 1 is a plan view in partial section and illustrates the pertinent fluid conduit passages and related structure of one form of the instant invention.

FIG. 2 is a diagrammatic sketch that illustrates the operation of the apparatus of FIG. 1.

Referring to FIG. 1 there is shown a horizontal frame plate on which is fixedly mounted two upstanding closely spaced parallel sheet guide plates 11 and 12. Plate 11 is formed with a bore for receiving one end of an emitter nozzle or tubular fitting 13, the latter being secured to plate 11 by any suitable means such as brazing or soldering as indicated at 14. A flexible hose or other ice conduit means indicated at 15 is connected to the other end of said fitting 13 and communicates with an air pressure source S2 through suitable valving (not shown). The sheet guide plate 12 is also formed with a bore for receiving one end of a receiver nozzle or tubular fitting 16, the latter being secured to plate 12 by any suitable means such as brazing or soldering. A flexible hose or other conduit means indicated at 17 is connected to the other end of the fitting 16 and communicates with an air pressure source S1 through suitable valving (not shown). The tubular fittings 13 and 16 are coaxially disposed and the effective outlet orifice sizes for said fittings are substantially equal. Operatively connected to the fitting 16 is a perpendicularly extending signal output tube 18 which is pneumatically coupled by means of a flexible hose or other conduit means indicated at 19 to a device CS to be controlled by the instant sensing apparatus.

As will be apparent the various above described structural elements may be integrally fashioned from one or more component parts or the composite sensing device illustrated in FIG. 1 may have a laminate construction wherein individual plates are appropriately grooved or otherwise formed so that when the plates are secured together in sandwich fashion the above described pneumatic conduit arrangement may be effectively obtained. Exemplary physical sizes for the various fluid conducting passages may be as follows: the inside diameters of the fittings 13 and 16 may be of an inch, while the inside diameter for the signal tube 18 may be somewhat less than of an inch. The operative gap distance between the opposed outlet openings in "nozzles 13 and 16 may be of an inch. It is to be understood that these dimensions are noted here for illustrative purposes and are not in any way to be considered as restrictive in nature.

The operation of the FIG. 1 system will be described in connection with the diagrammatic sketch shown in FIG. 2. The effective fluid pressure P2 from air pressure source S2 is made greater than the effective fluid pressure P1 from air source S1 so that a relatively strong first jet of air issues from nozzle 13 and an opposed but relatively weak second jet of air issues from nozzle 16. All of the air being exhausted by said opposed jets will escape laterally upon reaching the region between nozzles 13 and 16. Under these normal fluid flow conditions the impact recovery pressure from said first jet of air in fitting 16 at a point A just downstream from the signal tube 18 will 'be somewhat less than the effective pressure P1 (i.e. P1 less any line losses in the fitting 16) at point A. Hence under said normal conditions a pressure P3 greater than atmosphere pressure will exist in the signal output tube 18 and the resultant outward fluid flow through the latter will include only clean source air from S1. These normal operative pressure conditions will persist until an object to be sensed (such as a sheet 20, FIG. 2, that in being fed endwise by any suitable transport means along a sheet feed path 21, FIG. 1), is placed between the nozzles 13 and 16 so as to thereby disrupt or interfere with the normal air flow conditions between said nozzles. When the said first jet of air is thus effectively isolated from the second jet of air the fluid flow from nozzle 16 will no longer be dynamically opposed by the fluid jet from nozzle 13 and hence there will be a relatively free exhaust of air from nozzle 16 and a resultant pressure drop at point A; the air jet from nozzle 16 then freely moving away later-ally as illustrated by arrows 22 and 23, FIG. 2. The pressure drop in the region of point A will cause pressure P3 to drop to nearly zero (gage) and this pressure drop will constitute a signal which can be utilized to control the device CS which is to operate in association with the arrival of said sheet 20 at the sensing station that is effectively defined by the region between said nozzles 13 and 16. During this sensing of sheet 20 the 3 air flowing through the signal tube 18 will again include only clean source air from S1. When the sheet 29 is effectively removed from the sensing station the pressure P3 will again be restored to its normal higher level.

For the purposes of illustration an exemplary set of operating pressure conditions for the above dimensioned device may be as follows. Pressure P2 may have a value of 27 inches of water while pressure P1 may have a value of 7 inches of water. Under these pressure conditions the opposed jets of air issuing from nozzles 13 and 16 will be effectively opposing each other and will give rise to a normal positive pressure P3 in fitting 18 in order of 2-5 inches of water. It is to be understood that these specific pressure levels are mentioned for illustrative purposes only and that various other fluid pressure ranges and combination may be used.

One of the most significant operating characteristics of the instant sensing system is that air is always exhausting from all those system openings that are exposed to the surrounding atmosphere. This characteristic advantageously tends not only to continuously purge any foreign matter that may be already present in the fluid conduit system but also effectively prevents the entry into the system of external foreign particles from the atmosphere surrounding said openings. Hence foreign matter is at all times prevented from getting into and contaminating the fluid device CS that is operatively coupled to the signal output tube 18.

A sensing apparatus of the above described type has been constructed and tested and has been found to afford eflicient, reliable and maintenance free operation for extended periods of use.

Since many changes could be made in the embodiment of the invention as particularly described and shown herein without departing from the scope of the invention,

it is intended that this embodiment be considered as exemplary and that the invention not be limited except as warranted by the following claim.

What is claimed is: 1. A method of pneumatically sensing the presence of a sheet that is located in a predetermined location along a sheet feed path; comprising directing a first jet of air across said feed path at said location; directing a second jet of air in the opposite direction across said feed path at said location, said second jet of air being in effective opposition to said first jet of air and also having substantially the same initial cross-sectional area as that of said first jet of air; said first and second jets of air being supplied from two effectively separate fluid pressure sources, the fluid pressure source associated with said first jet of air having a higher pressure than that for the fluid pressure source associated with said second jet of air; detecting a drop in the upstream fluid pressure in said second jet of air with respect to the surrounding atmospheric pressure and independent of the pressure in said first jet of air and in response to the interference by said sheet of said first jet of air.

References Cited UNITED STATES PATENTS 3,240,410 3/1966 Jacobson 22622 X LOUIS R. PRINCE, Primary Examiner.

DAVID SCHONBERG, Examiner.

WILLIAM HENRY 11, Assistant Examiner. 

